Analyte detection is becoming increasingly important as a security and safety measure. Transportation, commercial, government, educational, and other facilities have a need for the sensitive and rapid detection of analytes, such as those that are indicative of explosives or other substances that pose a threat. In addition, in industrial, residential, and commercial settings, analyte detection can provide warning of particles that pose a health or safety risk. Example analytes to be detected include, for example, hazardous materials, including explosive-related materials, toxic industrial chemicals (TICS), narcotics, or chemical or biological agents.
Analysis instruments have been developed and are under development to meet the needs for detection of analytes. A nonlimiting example analysis instrument that is currently used in portable and larger forms is the Ion Mobility Spectrometer (IMS), such as the GE VaporTrace models. Speed and sensitivity are primary concerns in any such instruments. Researchers and manufacturers seek to improve the sensitivity of such analysis instruments.
A typical IMS device has separate particle and vapor modes. In particle mode, an assembly is affixed to the device to accept and desorb particles from a substrate such as a swab, for example, during baggage screening. The swab is inserted into the assembly, is heated to desorb any collected particulates, and the particulates are directed via vacuum into the instrument for analysis. Another assembly can be affixed to the device for vapor mode, in which the device collects vapors for analyte detection. This mode, for example, is commonly used to sample contained areas such as automobile trunks at the entrances to military facilities.
Preconcentrators offer the opportunity to enhance the performance of any type of analysis instrument by increasing the concentration of analyte in a volume of fluid sent for analysis. Generally, preconcentrators collect analyte over a period of time (during absorption) and then provide a concentrated fluid stream to the analysis device (during desorption). Desorption requires rapid heating, and microscale preconcentrators accordingly have advantages regarding thermal cycling and desorption, since heating for accomplishing desorption can be conducted quickly and with low power.
Microscale preconcentrators are disclosed in Manginell et al., U.S. Pat. No. 6,527,835, entitled Chemical Preconcentrator with Integral Thermal Flow Sensor, and in Manginell et al., U.S. Pat. No. 6,171,378, entitled Chemical Preconcentrator. The chemical preconcentrator used in that work is formed from a substrate having a suspended membrane, such as low-stress silicon nitride. This work incorporates a flow over design.
Successful microscale preconcentrators with a flow-through design are disclosed in U.S. Patent Application Publication No. 20050095722 (incorporated by reference herein), published May 5, 2005, and entitled “Microscale Flow Through Sorbent Plate Collection Device”, and in U.S. Patent Application Publication No. 20050226778, published Oct. 13, 2005, and entitled “Microscale Flow Through Sorbent Plate Collection Device”. The flow through design has a number of advantages, one of which is increasing contact between the analyte fluid flow and the sorbent in the collection area compared to typical flow over designs that would require creating a turbulent flow to match the level of analyte fluid-sorbent contact.
Lacking in the art is a practical and reliable interface that can easily and efficiently integrate a microscale preconcentrator with analysis instruments. A macroscale assembly for a large screen style preconcentrator has been developed and published by researchers at Sandia National Laboratories. See “Overview of Explosives Detection Research and in Development”, 16th Annual NDIA Security Technology Symposium & Exhibition, Jun. 26-29, 2000 John E. Parmeter, David W. Hannun, Kevin L. Linker, and Charles L. Rhykerd. This technology includes a large screen (a few inches in diameter) that accepts fluid (e.g., air) flow through a large round opening, and concentrated explosive molecules/partners via adsorption on the pleated screen. A custom block assembly attaches the preconcentrator to an IMS device.